1. Field of the Invention
This invention relates to a set of golf clubs. More particularly, the invention relates to a golf club set which comprises a plurality of differently numbered wood clubs and a plurality of differently numbered iron clubs.
2. Description of the Prior Art
As is well known, various types of golf clubs are commercially available which include wood clubs, iron clubs, putters, and so on. The wood clubs comprise No. 1 to No. 5 woods, while the iron clubs include No. 1 to No. 9 irons. The golfer brings all or selected ones of these clubs, and in play selects an optimum club for making a shot which he or she wants in a particular situation.
Golf clubs are often sold in a set although it is also possible to purchase any golf clubs separately at the golfer's option. Usually, such a golf club set includes No. 1 wood (driver), No. 3 wood (spoon), No. 4 wood (baffy), No. 3 to No. 9 irons, a pitching wedge, a sand wedge, and a putter. The golf club set may additionally include No. 5 wood (cleek) and No. 2 iron.
In general, average golfers often find difficulty in using long irons (usually No. 1 to No. 4 irons) because these irons are liable to erroneous shots. Such erroneous shots are partly due to the fact that the long iron is rather small in loft angle, sole thickness, head inertial moment and sweet spot area.
Another cause for difficulty in using the long iron resides in that it is relatively inflexible near the head end in comparison with the wood club. To more clearly explain this point, reference is now made to FIG. 8 illustrating the reverse deflection characteristics of the golf clubs included in a typical prior art golf club set.
In the graph shown in FIG. 8, the ordinate represents the reverse deflection (mm) of the club shafts included in the prior art golf club set, whereas the abscissa indicates the club number for both of the wood clubs and the iron clubs. The "reverse deflection" used herein is a parameter which indicates the head-end side flexibility of each club shaft and which is defined as displacement of a standard shaft point when a predetermined load is applied to the shaft at a predetermined distance from the head end of the shaft with the head end fixed. A specific method for measuring the reverse deflection will be described later in connection with the preferred embodiments of the present invention.
As clearly seen in FIG. 8, the reverse deflection of the wood clubs decreases proportionally along line X as the wood club number increases, and the reverse deflection of the iron clubs also decreases proportionally along line Y as the iron club number increases. However, the line X for the woods is much steeper in inclination than the line Y for the irons, so that there is no proportionality between the lines X and Y. Further, there is an abrupt decrease in reverse deflection from the No. 5 wood (the highest numbered or shortest wood in the set) to the No. 3 iron (the lowest numbered or longest iron in the set).
It is concluded from FIG. 8 that the reverse deflection of the long irons (the No. 3 and No. 4 irons) included in the prior art set is abruptly smaller than that of the wood clubs. In other words, the long iron club shafts of the prior art set are abruptly harder than the wood club shafts. Thus, when changing from a wood club to a long iron, the golfer will have a strange feel that the long iron is excessively hard in comparison with the wood club.
Basically, a long iron is used to make a relatively long shot, and therefore required to have shaft property (e.g. reasonable flexibility at the head-end side) generally similar to that of a wood club. In spite of such a requirement, the long iron of the prior art golf club set differs drastically in shaft property from the wood club. Due to this drastic difference, the golfer feels it difficult to use the long iron. Further, the head-end side of a club shaft must flex sufficiently to hit the ball high for an increased carry. However, the long iron shaft of the prior art set is excessively hard at the head-end side, so that it is difficult for an average golfer to realize a long carry with the prior art long iron.